The purpose of this investigation is to elucidate the function of basophils and mast cells in cell mediated hypersensitivity reactions, particularly with regard to an understanding of the role of these cells in immunologic tumor rejection. The experiments proposed will make use of a tissue culture system and a combined biochemical morphologic, and immunologic approach to determine: (1) Whether sensitized lymphocytes or their products affect histamine synthesis and/or release in basophils/mast cells. (2) The mechanism of mediator release from basophils/mast cells under circumstances which avoid explosive degranulation. (3) The effects of basophils/mast cells and their pharmalogic mediators on tumor target cells.